H I S i s the first symposium on synthetic lubricating oils sponsored by the Division OF Petroleum Chemistry of the American Chemical Society. Discussion OF synthetic lubricants i s particularly appropriate at this time because of the tremendous strides that have been made i n this field during the past d e c a d e b o t h From the experimental and From the commercial viewpoint. W i t h i n the past 10 years, certain esters and p o l y g l y c o l ethers have been developed as commercial synthetic lubricants. A decade ago it would have been difficult to predict the rapid commercialization of silicones, fluorocarbons, and chlorofluorocarbons. The interest i n this symposium i s an acknowledgment of tho excellent work being done i n the field of synthetic lubricants. From a research viewpoint, synthetic lubricants are old. A l m o s t 75 years ago, Friedel and Crafts [Compt. rend., $4, 1 9 3 8 (1 877)J reported that they obtained a viscous hydrocarbon oii on treating amyl chloride with aluminum or aluminum chloride and hydrolyzing the resulting complex. Two years later Balsohn [BUN.SOC. shim., 31 , No. 2, 5 3 9 (1879)l reported that ethylene reacts with aluminum chloride to give a complex which on subsequent hydrolysis yields a lubricating oil. Since then extensive research on various types of synthetic lubricants has been reported in the literature. The first commercial synthetic lubricating oils were manu6actured and marketed i n 1929 by the Standard Oil Company (Indiana). The process and the properties of the products were described by Sullivan, Voorhees, Neeley, and Shankland beFore the Division of Petroleum Chemistry at the 81st M e e t i n g OF the American Chemical Society, A p r i l 1931. Since this development represents a milestone i n the story OF synthetic lubricating oils, it i s appropriate for us to review a n d supplement briefly their work as reported earlier
[IND.ENG. CHEM., 23, 604 (1 93111.
These synthetic lubricating o i l s were made by polymerizing cracked wax with aluminum chloride. The l i q u i d fraction of the cracked wax, having 5 to 1 5 carbons pet molecule, was the feed stock For the polymerization reaction, which was carried out by contacting the cracked wax with 3% by weight OF aluminum chloride et 1 3 0 " to 135 O F. For a p e r i o d of 30 hours. A f t e r settling, the aluminum chloride complex was withdrawn and the hydrocarbon layer was neutralized with caustic. The oils were finished by steam stripping and percolation through clay. Products were manufactured having viscosities at 210" F. of 100 and 200 S.S.U. The commercial process utilized available thermal cracking equipment of the coil-and-drum type, built for the cracking o f gas oils. The polymerization step was carried out in a specially designed unit i n which t w o 9000-gallon vessels served as reactors. A g i t a t i o n was accomplished by circulation through centrihgal pumps. As optimum conditions for cracking the wax could not b e maintained in the gas-oil cracking equipment employed, commercial operation of the process was somewhat less successful than had been predicted by laboratory investigations. Viscosity index of the oils was 95 to 100, whereas 105 to 110 was expected. Based on the wax charged, the over-all y i e l d of o i l s was 30%, as compared with t h e 50% realized in the laboratory. It was recognized that inability to control contact time i n the cracking operation reduced the olefin content a n d increased side reactions, and thus led t o lower yields OF slightly inFerior oils.
A l t h o u g h these oi!s were not outstanding by today's standards, they were unique i n i 9 3 0 i n khat they were wax-Free and had excellent color and an extremely l o w carbon-forming tendency. They attracted considerable interest For specialty uses, such as shock absorber, ice machine, and hydraulic oils [Sullivan e t al., S.A.E. Journa!, 29, 40 (1 936 11. Price appeared to b e the main Factor responsible for the limited acceptance of these synthetics as premium motor oils. Considerable attention was given to possible application as aircraft engine oils and, although this use did not reach commercialization, the laboratory data l o o k e d promising. A b o u t 3 million gallons OF these oils were manufactured before the operation was abandoned. The relatively high cost of the products, due t o the steadily increasing value of the wax, was the major factor in the decision to discontinue the process. Today two United States petroleum companies are manufacturing and marketing synthetic hydrocarbons in the lubricating o i l range. These oils are made by the catalyfic polymerization of a butene fraction and are isobutene-n-butene copolymers. They are evailable in viscosities ranging upward from 100 S.S.U. at 100" F. Although limited quantities of these products find applications a5 specialty lubricants, the principal uses are i n adhesives and plasticizers and as chemical Intermediates. Viscous polymers of ethylene OP propylene are not being offered commercially i n the United States, although ethylene polymers were being made for use as lubricants i n Germany during W o r l d War 11. What does the future h o l d For synthetic lubricants? Iam convinced that they w i l l occupy an increasingly important place i n the field of specialized lubrication. Their lubricating qualities combined with one or more novel properties-such as the nonFlammability of the silicones, the high flash points of the esters, and the excellent thermal the individual synthetic lubristability of the Fluorocarbons-make cants particularly valuable For specific apjllications. As long as the price of these synthetics continues to b e high, we can expect that these oils w i l l command o n l y a vary small percentage of the market. Lubricant demands are such, however, that even a small fraction of the total market i s a highly attractive field. The volume of oils and greases produced annually i n the United States i s about 50 million barrels; if o n l y 1% were synthetics, the volume of synthetic lubricants manufactured would equal the annual production of ethylene glycol. There i s every reason t o believe that synthetic l i q u i d fuels w i l l not b e a major factor in the nation's fuel supply for many years. Even aFter our l i q u i d fuels are largely OF synthetic origin, many more years would elapse before a shortage OF crude o i l might Force us to resort to the more general use OF synthetic oils for lubrication. Under such circumstances, polymerization of synthetic olefinspossibly derived from a hydrocarbon synthesis process-would proba b l y provide the bulk lubricants of the 6uture. Synthetic hydrocarb o n polymers could then b e made at costs not much higher than those For natural oils. Nonhydrocarbon synthetic lubricants certainly would b e used for those applications in which the hydrocarbon polymers prove unsatisfactory. It i s reasonable to assume that this would b e a sizable percentage of the total market.
B. H. SHOEMAKER
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